Sensitive electron-capture gas-liquid chromatographic assay for the DE-ethylated metabolite of metoclopramide

Abstract A procedure is described for determining 4-amino-5-chloro-2-methoxy-N-(2-ethylaminoethyl)benzamide, a metbaolite formed by de-ethylation of metoclopramide, in urine from rats. The sample is extracted (at pH ≈ 13) with chloroform and, after treatment with heptafluorobutyric anhydride, derivatives of the extracted compounds are analyzed by gas-liquid chromatography, with electron-capture detection and diazepam as internal standard. The drug and its metabolite are separated, and the latter can be determined in the range 0.4 to 1.85 μg/ml in the sample. The behaviour of the metabolite during chemical-ionization and electron-impact mass spectrometry is discussed.